A number of devices are intended to identify and/or discriminate coins or other small discrete objects. One example is coin counting or handling devices, (such as those described in U.S. patent application Ser. No. 08/255,539, now U.S. Pat. No. 5,564,546, and its continuation application Ser. Nos. 08/689,826, 08/237,486, now U.S. Pat. No. 5,620,079 and its continuation Ser. No. 08/834,952, filed Apr. 7, 1997, and 08/431,070, all of which are incorporated herein by reference). Other examples include vending machines, gaming devices such as slot machines, bus or subway coin or token "fare boxes," and the like. Preferably, for such purposes, the sensors provide information which can be used to discriminate coins from non-coin objects and/or which can discriminate among different coin denominations and/or discriminate coins of one country from those of another.
Previous coin handling devices, and sensors therein, however, have suffered from a number of deficiencies. Many previous sensors have resulted in an undesirably large proportion of discrimination errors. At least in some cases this is believed to arise from an undesirably small signal to noise ratio in the sensor output. Accordingly, it would be useful to provide coin discrimination sensors having improved signal to noise ratio.
Many previous coin handling devices, and associated sensors, were configured to receive only one coin at a time, such as a typical vending machine which receives a single coin at a time through a coin slot. These devices typically present an easier coin handling and sensing environment because there is a lower expectation for coin throughput, an avoidance of the deposit of foreign material, an avoidance of small inter-coin spacing (or coin overlap), and because the slot naturally defines maximum coin diameter and thickness. Coin handlers and sensors that might be operable for a one-at-a-time coin environment may not be satisfactory for an environment in which a mass or plurality of coins can be received in a single location, all at once (such as a tray for receiving a mass of coins, poured into the tray from, e.g., a coin jar). Accordingly it would be useful to provide a coin handler and/or sensor which, although it might be successfully employed in a one-coin-at-a-time environment, can also function satisfactorily in a device which receives a mass of coins.
Many previous sensors and associated circuitry used for coin discrimination were configured to sense characteristics or parameters of coins (or other objects) so as to provide data relating to an average value for a coin as a whole. Such sensors and circuitry were not able to provide information specific to certain regions or levels of the coin (such as core material vs. cladding material). In some currencies, two or more denominations may have average characteristics which are so similar that it is difficult to distinguish the coins, for example, it is difficult to distinguish U.S. dimes from pre-1982 U.S. pennies, based only on average differences, the main physical difference being the difference in cladding (or absence thereof). In some previous devices, inductive coin testing is used to detect the effect of a coin on an alternating electromagnetic field produced by a coil, and specifically the coin's effect upon the coil's impedance, e.g. related to one or more of the coin's diameter, thickness, conductivity and permeability. In general, when an alternating electromagnetic field is provided to such a coil, the field will penetrate a coin to an extent that decreases with increasing frequency. Properties near the surface of a coin have a greater effect on a higher frequency field, and interior material have a lesser effect. Because certain coins, such as the United States ten and twenty-five cent coins, are laminated, this frequency dependency can be of use in coin discrimination, but, it is believed, has not previously been used in this manner. Accordingly, it would further be useful to provide a device which can provide information relating to different regions of coins or other objects.
Although there are a number of parameters which, at least theoretically, can be useful in discriminating coins and small objects (such as size, including diameter and thickness), mass, density, conductivity, magnetic permeability, homogeneity or lack thereof (such as cladded or plated coins), and the like, many previous sensors were configured to detect only a single one of such parameters. In embodiments in which only a single parameter is used, discrimination among coins and other small objects was often inaccurate, yielding both misidentification of a coin denomination (false positives), and failure to recognize a coin denomination (false negatives). In some cases, two coins which are different may be identified as the same coin because a parameter which could serve to discriminate between the coins (such as presence or absence of plating, magnetic non-magnetic character of the coin, etc.) is not detected by the sensor. Thus, using such sensors, when it is desired to use several parameters to discriminate coins and other objects, it has been necessary to provide a plurality of sensors (if such sensors are available), typically one sensor for each parameter to be detected. Multiplying the number of sensors in a device increases the cost of fabricating, designing, maintaining and repairing such apparatus. Furthermore, previous devices typically required that multiple sensors be spaced apart, usually along a linear track which the coins follow, and often the spacing must be relatively far apart in order to properly correlate sequential data from two sensors with a particular coin (and avoid attributing data from the two sensors to a single coin when the data was related, in fact, to two different coins). This spacing increases the physical size requirements for such a device, and may lead to an apparatus which is relatively slow since the path which the coins are required to traverse is longer.
Furthermore, when two or more sensors each output a single parameter, it is typically difficult or impossible to base discrimination on the relationship or profile of one parameter to a second parameter for a given coin, because of the difficulty in knowing which point in a first parameter profile corresponds to which point in a second parameter profile. If there are multiple sensors spaced along the coin path, the software for coin discrimination becomes more complicated, since it is necessary to keep track of when a coin passes by the various sensors. Timing is affected, e.g., by speed variations in the coins as they move along the coin path, such as rolling down a rail.
Even in cases where a single core is used for two different frequencies or parameters, many previous devices take measurements at two different times, typically as the coin moves through different locations, in order to measure several different parameters. For example, in some devices, a core is arranged with two spaced-apart poles with a first measurement taken at a first time and location when a coin is adjacent a first pole, and a second measurement taken at a second, later time, when the coin has moved substantially toward the second pole. It is believed that, in general, providing two or more different measurement locations or times, in order to measure two or more parameters, or in order to use two or more frequencies, leads to undesirable loss of coin throughput, occupies undesirably extended space and requires relatively complicated circuits and/or algorithms (e.g. to match up sensor outputs as a particular coin moves to different measurement locations).
Some sensors relate to the electrical or magnetic properties of the coin or other object, and may involve creation of an electromagnetic field for application to the coin. With many previous sensors, the interaction of generated magnetic flux with the coin was too low to permit the desired efficiency and accuracy of coin discrimination, and resulted in an insufficient signal-to-noise ratio.
Many previous coin handling devices and sensors had characteristics which were undesirable, especially when the devices were for use by untrained users. Such previous devices had insufficient accuracy, short service life, had an undesirably high potential for causing user injuries, were difficult to use, requiring training or extensive instruction, failed, too often, to return unprocessed coins to the user, took too long to process coins, had an undesirably low throughput, were susceptible to frequent jamming, which could not be cleared without human intervention, often requiring intervention by trained personnel, could handle only a narrow range of coin types, or denominations, were overly sensitive to wet or sticky coins or foreign or non-coin objects, either malfunctioning or placing the foreign objects in the coin bins, rejected an undesirably high portion of good coins, required frequent and/or complicated set-up, calibration or maintenance, required too large a volume or footprint, were overly-sensitive to temperature variations, were undesirably loud, were hard to upgrade or retrofit to benefit from new technologies or ideas, and/or were difficult or expensive to design and manufacture
Accordingly, it would be advantageous to provide a coin handler and/or sensor device having improved discrimination and accuracy, reduced costs or space requirements, which is faster than previous devices, easier or less expensive to design, construct, use and maintain, and/or results in improved signal-to-noise ratio.